The subject of this thesis is a case study of the expansion of an extremist sect in Medieval Islam. The popular name of this sect has made an indispensable contribution to almost every language of western Europe, and is still able to conjure up a range of fantastic associations. Medieval chronicles, both Latin and Arabic, depicted these sectaries as a desperate band of fanatical killers of kings and princes, and Medieval travellers gave currency to tales of drugs and paradisaical gardens used to induce young men to become devotees, of unhesitating death-leaps to impress visitors with their blind obedience to their leader: their unswerving devotion has been a source of allusion for Provencal love poems and as great a poet as Dante, while at least one “modern” writer has seen in them the archetypal revolutionary secret society, the embodiment of all evil, duplicity, and moral corruption. (J. von Hammer, Geschichte der Assassinen aus morgenlandischen Quellen, Stuttgart, 1818, English translation, The History of the Assassins, by O.C. Wood, London, 1835.) The legend which has grown up around the so-called sect of the Assassins easily obscures their historical reality. Accordingly, the first two chapters of this thesis attempt to indicate the outlines of this reality, to dispel any lingering wisps of legend, to trace the movement's heritage in Islam, showing its origins, its aims, the nature of its beliefs and organization and a little of its early history in Persia. The Persian Nizari Ismaᶜilis, as they should properly be called, expanded their propaganda campaign into Syria at about the same time as the First Crusade, in the closing years of the eleventh century. The comparison is instructive; the Nizaris were only just securing permanent bases in Syria by the time the Crusaders had lost their first major territorial acquisition, the principality of Edessa, in 1144. Why did the sectaries take so long to get established? Was it simply because of the strength of the opposition they met, or were there unforeseen disadvantages for them in the Syrian situation? Were they perhaps in some measure at fault themselves, in their handling of obstacles and reverses? The purpose of this thesis is to investigate the problem of the Nizari establishment in Syria, to find an explanation for its long delay. Though much has been written about the “Syrian Assassins”, probably a reflection of their proximity to the crusaders, the early phase of their establishment has not received the detailed examination it deserves. By far the best account is that contained in the chapter by Bernard Lewis entitled "The Ismāᶜīlites and the Assassins" in A History of the Crusades, editor-in-chief, K. M. Setton, volume i, The First Hundred Years, ed. M. W. Baldwin, published by the University of Pennsylvania, (Philadelphia, 1955). The footnotes here are much fuller than those for Chapter 5 of Lewis's more recent The Assassins, A Radical Sect in Islam (London, 1967), which, aside from a few fresh items, is a word-for-word repetition of his chapter in the Pennsylvania History. The best monograph on the whole sect was written by the late Marshall G. S. Hodgson; The Order of the Assassins; the Struggle of the Early Nizârî Ismâᶜîlîs against the Islamic World (The Hague, 1955). His focus, naturally enough, is on the parent Persian sect, and he candidly admits that for Syrian affairs he has relied heavily on already-published studies. (See pp.89, n.20; 185, n.1). Recent work by Ismaᶜili scholars in the Middle East has dealt with the Syrian Nizaris, but centres mainly on the rule of the famous "Old Man of the Mountain", Rashid al-Din Sinan (c.1162-1193). The writings of ᶜĀrif Tāmir and Muṣṭafā Gālib in particular are said to enhance our understanding of the Nizaris in Syria (see Lewis's remarks in Arabica, XII (1966), p.226) but being in Arabic, they are for the moment closed to me. The most recent unpublished study in English betrays a similar tendency to concentrate on Sinan's rule. In his Ph.D. thesis (Durham, 1963), “The Syrian Ismāᶜīlis at the time of the Crusades”, Nasseh Ahmad Mirza treats the period of establishment very briefly in an introduction which adds virtually nothing to Lewis or Hodgson. To my mind, these works leave unanswered the question I have set myself in this thesis; how did the Nizaris establish themselves in Syria and why did they take so long to achieve permanent establishment?